1. Field of the Invention
This invention relates to apparatus mountable on motor vehicles, such as pickup trucks, vans and the like, for lifting and moving loads between the beds or cargo receiving space of such vehicles and the ground beyond and beneath an open extremity of the load receiving space through a zone of clearance limited by the structure of the vehicle itself.
My improved apparatus, by virtue of the nature and arrangement of the cooperating mechanical structures employed therein, achieves relative simplicity and economy of fabrication and installation as compared with conventional hoisting equipment, together with ease, reliability and safety of operation even by a single individual, and avoids encroachment upon the often limited cargo space typically available in the class of vehicles for which it is optimumly adapted.
2. Description of the Prior Art
The types of prior hoisting or load lifting equipment mountable upon motor vehicles for use in moving loads into and out of the cargo space within the vehicle of which I am aware fall into three general categories.
First, some trucks have been equipped with elevatable tail gates, which essentially serve as a vertical elevator onto which a load may be intermediately transferred and raised or lowered in the course of moving it between the cargo space of the truck and ground level. Such elevator structures typically employ hydraulic cylinders for supporting the load carrying assembly during movement along a vertical path to which it is confined by some form or track or guide mechanism that also serves to prevent tipping. By its very nature, however, that type of equipment is best incorporated into the truck during manufacture of the latter and is difficult and expensive, if not practically impossible, to add onto many existing vehicles not originally so equipped.
Secondly, some open top trucks have been equipped with crane-like hoists typically involving some sort of often rotatable base structure carrying a boom that is pivotally mounted on the base structure for angular swinging movement in an elevational plane by a hydraulic cylinder or the like, together with a winch located on the base structure or an adjacent part of the boom having its flexible element extending along the boom and passing over a pulley adjacent the distal end of the boom. Such crane-like equipment, however, usually encroaches on the space otherwise available for cargo, must be relatively heavy and expensively fabricated with a relatively long boom for effectively handling "off the rear" loading and unloading, requires some special skill for safe operation in "off the rear" load handling, and, of course, is ill-adapted or impossible to use with vehicles such as vans having closed tops over cargo spaces provided with relatively restricted clearance for loads only at one extremity thereof.
Thirdly, some trucks, especially of the flat bed type having no obstructions or only easily removable posts around the periphery of the cargo area, have been equipped with a form of hoist involving an upstanding base or pillar structure having a stiff, fixed length boom extending horizontally from the top of the base structure and rotationally swingable in a horizontal plane, together with a winch located on the base structure or an adjacent part of the boom having its flexible element extending along the boom and passing over a pulley adjacent the distal end of the boom. Such hoists, however, aside from being primarily adapted for "off the side" load handling operations when the base structure is prudently centered relative to the width of the truck, also suffer from essentially the same disadvantages as mentioned for crane-like hoists.
I am not acquainted with any prior load lifting and moving equipment mounted on trucks, which I believe to be of a type fully satisfactory and practical, operationally and economically, for installation and use upon motor vehicles such as existing conventional pickup trucks, vans and the like by the persons who typically utilize such vehicles.